Gerold, I guess you must have some insight that I do not - perhaps you could enlighten us?
It seems clear to me from all the posts I have read in this and other forums that this is an ongoing problem, with new purchasers complaining about excess dust or oil or both - many new users are still posting pictures as proof.
Users who have returned their cameras are also reporting a mixed bag of results with some reasonably happy after multiple shutter replacements and others who still have problems.
Even allowing for the extreme reports at both end of the scale on this problem, an average person would have to have some strong doubts that Nikon have fixed the D600 dust and oil problem.
So Gerold, please provide the proof of your statement.